ABSTRACT/SUMMARY: Accumulating evidence has demonstrated that exposure to man-made chemicals can disrupt human reproductive health. Elucidation of the relevant mechanisms is critical for preventative and treatment strategies. The goal of the proposed work is to investigate the role of endocrine disrupting chemicals (EDCs) in modulating tryptophan catabolism as a novel mechanism of environmental exposure-induced pregnancy failure and complications. Tryptophan catabolism is a regulator of maternal immune tolerance during pregnancy. Failure to degrade tryptophan in the pregnant mother is linked to a significant proportion of human miscarriages, preeclampsia, and premature labor. A key event of this pathway is the activation of the placental Ido1 gene that encodes for a major tryptophan-degrading enzyme. Our laboratory has shown that in utero exposure to a representative EDC, tetrabromobisphenol A (TBBPA), reduces placental Ido1 gene and protein expression, and is linked to increased rate of fetal resorption. In this proposal, we wish to investigate whether in utero exposure to TBBPA alters pregnancy outcomes by perturbing tryptophan catabolism and reducing maternal-fetal immune tolerance. We will expose female mice to environmentally relevant doses of TBBPA (i.e., 5, 50, and 500 g/kg bw/day) prior to mating, during mating, and throughout pregnancy, and analyze the pregnant mice and conceptuses. We wish to determine if exposures are linked to reduced maternal immunity by analyzing a subset of immunosuppressive T cells called ?regulatory T cells? or ?Tregs?. Using flow cytometry, we will determine Treg number in the decidua and uterus of controls and exposed pregnant mice. Elevated Tregs favor pregnancy maintenance, so therefore we anticipate that TBBPA-exposed mice have reduced Tregs. To determine if reduced Treg number is causatively linked to increased rate of fetal loss in TBBPA-exposed pregnant mice, we will perform an adoptive transfer study using Tregs from donor Foxp3-GFP mice. Additionally, we will perform liquid chromatography and mass spectrometry-based assays to measure levels of tryptophan and its catabolites in the pregnant dam, fetus, and placenta during sequential stages of pregnancy. We wish to elucidate whether TBBPA-induced effects on maternal immunity and pregnancy outcomes are linked to abnormal levels of catabolites. Finally, our preliminary studies show that the Ido1 gene is subject to genomic imprinting. In addition to characterizing molecular regulation of the locus, we will investigate how TBBPA exposure misregulates Ido1 locus activity through analyses of DNA methylation and/or posttranslational histone modifications by using quantitative real time PCR, bisulfite sequencing, and chromatin immunoprecipitation. !